Centralizers may be installed on tubulars, generally as part of a drill or casing string in an oilfield context, to provide an annular standoff between the tubulars and a surrounding tubular (e.g., wellbore). Centralizers can provide this standoff using blades or ribs that extend radially outward from the tubulars. One type of centralizer employs flexible, bow-shaped ribs or “bow springs,” which resiliently engage the surrounding tubular. Such bow-spring centralizers may be capable of providing a standoff across a range of diameters of the wellbore, and may collapse radially to pass through restrictions or obstructions (i.e., areas of reduced diameter in the wellbore).
Various processes, including heat treating and tempering, are employed to give the bow springs the resiliency that allows them to elastically deform when confronted with reductions in wellbore diameter, and to spring back once these restrictions are passed. However, the first time the centralizer passes through a restriction, the bow springs may yield and experience an amount of plastic deformation. This yielding can affect the starting, running, and/or restoring forces, among other things, which characterize the performance of the bow springs, according to industry standards. Further, such yielding can potentially compromise the integrity of the bow spring, which may result in off-design performance, shortened life, and/or failure.
Further, accurate information regarding the performance of a particular centralizer in actual wellbore conditions may be difficult to collect, prior to running the centralizer into the wellbore. Current standards allow a tolerance of 1% in the diameter of the tubular, which defines, or at least contributes to, a radial end range for collapse of the bow springs of the centralizer. Especially in large diameter tubing applications, this tolerance may be sufficient to affect the yielding of the centralizer. As such, measuring the characteristics of the centralizer in a test stand may be inaccurate, as the actual dimensions of the tubular upon which the centralizer will be disposed may not be known beyond the standard tolerance. Thus, uncertainties as to the performance of the centralizer in the wellbore may exist, despite testing efforts.